The present invention relates to a process for soil improvement and a process for increasing the assimilation of nitrogen by higher plants. The invention further relates to a composition for soil improvement and thus indirectly for promoting the yield capacity of higher plants, in particular crop plants, taking particular account of legumes.
As is known, the plant hormone ethylene gives rise in crop plants and other higher plants to a number of reactions which, based on agricultural and horticultural practice and on the storage and transport of plant products, in some cases have a positive effect and in some cases an adverse effect. It is therefore common practice to make controlled interventions in the processes which can be influenced by ethylene using suitable active compounds. To differentiate, there are essentially the following possibilities here:
1. Increasing the ethylene level in the tissue of the plants by
1.1 treating with ethylene or acetylene, which often has a similar effect to ethylene;
1.2 treating with ethylene-releasing compounds, eg. ethephon (active compound 1.2), etacelasil (see xe2x80x9cThe Pesticide Manualxe2x80x9d, 9th edition, No. 5680 and 5640),
1.3 treating with compounds from which ethylene is released by plant metabolism, eg. 1-aminocyclopropane-1-carboxylic acid;
1.4 treating with ethylene-inducing compounds, eg. 2,4-dichlorophenoxyacetic acid in the case of tomatoes.
2. Reducing the ethylene concentrations occurring in the plant tissue by
2.1 decomposing the ethylene present in the surrounding atmosphere (eg. by KMnO4);
2.2 adsorbing the ethylene occurring in the surrounding atmosphere or in the plant [eg. by Buckminsterfullerene (Leshem et al., 1993, Buckminsterfullerenes (C60 bucky-ball) inhibition of ethylene release from senescing legume foliage and cut carnations, Current Plant Science and Biotechnology in Agriculture 16: 174-181) or polymers of vinylquinoline (Sakota et al., 1993, Ethylene formation inhibitors containing vinylquinoline polymers, JP 05,199,835)]
2.3 inhibitors of plant ethylene biosynthesis. The following groups are to be differentiated here with respect to their suspected intervention in ethylene biosynthesis:
2.3.1 inhibitors of the conversion of S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylic acid, such as
derivatives of vinylglycine [inter alia rhizobitoxin, aminoethoxyvinylglycine (active compound 2.3.1.1)]
hydroxylamine derivatives [inter alia L-canaline, aminooxyacetic acid (active compound 2.3.1.2)]
oxime ether derivatives eg. such as mentioned in EP-A 0 243 834 ({circumflex over (=)} U.S. Pat. No. 4,744,811) or EP-A 501 326;
2.3.2 inhibitors of the conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene such as
Co++ and Ni++ ions
decouplers of oxidative phosphorylation, eg. 2,4-dinitrophenol
nonionic detergents based on polyoxyethylenesorbitan monolaurate (eg. Tween(copyright) 20=active compound 2.3.2.1), alkylphenoxypolyethoxyethanol (eg. Triton(copyright) X-100=active compound 2.3.2.2), synthetic fatty alcohols (eg. Lutensol(copyright) AO 10=active compound 2.3.2.3) or sodium dodecyl sulfate (=active compound 2.3.2.4)
free radical scavengers such as n-propyl gallate
polyamines such as putrescine (=tetramethylenediamine, active compound 2.3.2.5) and derivatives derived therefrom such as spermine (NH2(CH2)3NH(CH2)4NH(CH2)3xe2x80x94NH2, active compound 2.3.2.6) or spermidine (mono-xcex3-aminopropylputrescine, active compound 2.3.2.7)
structural analogs to 1-aminocyclopropane-1-carboxylic acid such as xcex1-aminoisobutyric acid (active compound 2.3.2.8) or 1-aminocyclopropene-1-carboxylic acid (Pirrung and Trinks, 1989, Ethylene biosynthesis. Aminocyclopropenecarboxylic acid, Journal of the Chemical Society, Chemical Communications, 857-859)
salicylic acid (active compound 2.3.2.9) (Romani et al., 1989, Salicylic acid inhibition of ethylene production by apple discs and other plant tissues, Plant Growth Regulation 8: 63-69)
inhibitors of cytochrome P-450-dependent monooxygenases [eg. tetcyclacis (active compound 2.3.2.10), 1-phenoxy-3-azol-1-yl-4-hydroxy-5,5-dimethylhexane (active compound 2.3.2.11), epoxyconazole (2RS,3RS-1-[3-2-chlorophenyl)-2-(4-fluorophenyl)-oxiran-2-ylmethyl]-1H-1,2,4-triazole, (active compound 2.3.2.12) (Siefert et al., 1994, Are ethylene and 1-aminocyclopropane-1-carboxylic acid involved in the induction of chitinase and xcex2-1,3-glucanase activity in sunflower cell suspension cultures?, Planta 192: 431-440)
3. Inhibition of ethylene action by substances which block the site of reaction (ethylene receptor):
Examples known here are CO2, silver ions, 2,5-norbornadiene, 3-amino-1,2,4-triazole and cis-propenylphosphonic acid.
As far as can be taken from the literature, the processes mentioned in 2.1 and 2.2 are employed mainly in storage rooms, eg. for fruit, vegetables or cut flowers. The processes indicated in 2.3 on the other hand comprise a plant treatment and are aimed at an immediate change of the ethylene status in the tissue of the higher plant. Methods to reduce the ethylene content in the soil, ie. in the soil atmosphere, however, are unknown in practice.
Its an object of the present invention to find processes by which the soil in the root area of plants can be improved and by which, as a result, the growth and/or the assimilation of N2 from the air by higher plants can be increased. The achievement of this object should in the end result in causing a higher yield capacity of crop plants, in particular of legumes such as eg. beans, peas, lucerne, groundnuts, soybeans etc.
We have found that this object is achieved by a process for soil improvement which comprises carrying out a reduction of microbially produced ethylene in the soil by bringing compounds which bind ethylene or inhibit ethylene biosynthesis in higher plants between S-adenosyl-L-methionine and 1-aminocyclopropanecarboxylic acid or 1-aminocyclopropane-1-carboxylic acid and ethylene respectively into the soil zone relevant for the root growth of higher plants and allowing them to act there on the soil microorganisms.
A process for increasing the assimilation of nitrogen by higher plants has furthermore been found, which comprises adding to the soil zone relevant for root growth compounds which bind ethylene or in higher plants inhibit ethylene biosynthesis between S-adenosyl-L-methionine and 1-aminocyclopropane-1-carboxylic acid or 1-aminocyclopropanecarboxylic acid and ethylene respectively.
The invention further relates to compositions for soil improvement, by reducing microbially produced ethylene in the soil, which contain compounds of the abovementioned groups or mixtures thereof and the use of these compositions for soil improvement.
Increased ethylene concentrations in the soil lead in most crop plants to reduced growth and thus to depressed yields. Only rice and a few other plants suited to growth in wet soils or in water react in a less sensitive manner in this respect.
Inhibition of root growth is only to be expected according to M. B. Jackson, Ethylene in root growth and development, in: The Plant Hormone Ethylene, Mattoo, A. K. and Suttle, J. C. (eds.), CRC Press, Boca Raton, 1991, pp. 159-182, when in stress situations excessive ethylene formation by the root tissue occurs or when the endogenously formed ethylene accumulates as a result of reduced gas exchange in the area of the roots. Under field conditions, adverse effects on root growth of this type can occur when the gas exchange of the soil is inadequatexe2x80x94eg. as a result of severe wetness. On the one hand, the ethylene formed by the root itself can then accumulate, but on the other hand under these conditions there is the risk that concentration of microbially produced ethylene can occur.